The invention is based on a method for activating a device for the relative rotation of a shaft and on a device for the relative rotation of the camshaft of an internal combustion engine relative to the drive wheel of the camshaft rotatably arranged on the same. In known devices and methods of this type for the activation, a piston/cylinder device is acted upon by means of a control valve, and the piston displaces a coupling element which is supported in a recess of the camshaft. On the coupling element, which is in engagement with the camshaft, there are straight and helical teeth which, when the setting piston is displaced, rotate the camshaft relative to the drive wheel. A hydrostatic pump driven by the camshaft supplies the pressure medium necessary for the adjustment of the setting piston. The setting piston is subjected to pressure at both ends, one end being continually subjected to the pressure generated by the pump. The pressure on the other end of the piston is varied, as a function of certain control parameters, by the control valve by pressure reduction or by permitting pressure medium to flow away (de-activation). A method of this type and a device of this type are very complex and also, therefore, complicated and, more particularly, require a high expenditure of energy.